Substrate structure with spatial arrangement configured for coupling of surface plasmons to incident light

ABSTRACT

Embodiments of the disclosure provide a substrate structure for an integrated circuit (IC) structure, including: a first dielectric layer positioned above a semiconductor substrate; a first plurality of trenches extending at least partially into the first dielectric layer from an upper surface of the first dielectric layer; and a first metal formed within the first plurality of trenches, wherein a spatial arrangement of the first plurality of trenches causes coupling of surface plasmons in the first metal to at least one wavelength of an incident light.

BACKGROUND Technical Field

The present disclosure relates to integrated circuit (IC) structures foroverlay alignment in IC fabrication including multiple patterninglithography. More particularly, the present disclosure relates toforming trenches that allow for coupling of surface plasmons in a metalto incident light. Embodiments of the present disclosure include varioussubstrate structures using plasmon-resonant structures, and methods offorming the same.

Related Art

Integrated circuit fabrication requires forming large numbers ofinterconnected devices, such as transistors, resistors, capacitors, anddiodes on the surface of a semiconductor substrate material. Thesedevices are formed in part by selectively depositing and removingmultiple design layers of different materials, e.g., semiconductors,insulators, photoresists, masks, etch stop layers, and metals.Fabrication of functional and reliable ICs depends at least partially onaccurate alignment between each of these design layers. Some of thesedesign layers may be formed using multiple patterning lithography. Astechnology nodes continue to shrink, ensuring accurate alignment betweenlayers has become paramount to the fabrication of functional andreliable ICs.

Double patterning lithography is one type of multiple patterninglithography technology that has been in use for some time. Doublepatterning lithography generally involves placing shapes that are withinthe same design layer but too close to each other to be assigned to thesame mask layer onto two different mask layers in order to satisfyspacing requirements specified in the design layout. These two differentmask layers are then used to print one design layer. Other multiplepatterning lithography options such as multiple patterning (e.g., tripleor quadruple patterning) lithography may use more than two masks.Accurate alignment between the multiple mask layers is also one ofseveral important factors in fabrication of functional and reliable ICs.

Accurate alignment between design layers and mask layers may beaccomplished by several means. One of these is forming one or moresubstrate structures, which may not include functional components of anelectronic circuit, on the partially fabricated IC as it is beingprocessed. Lithography scanners may image the substrate structures andadjust the positions of the partially fabricated IC and the mask reticleto bring them into proper alignment with one another before printing. Inaddition, substrate structures may be imaged after a series offabrication operations to detect if misaligned features are present,allowing a determination to be made to continue fabrication, conductrework operations, or discard a defective IC.

One type of substrate structure, sometimes known more specifically as an“overlay mark,” may be composed of several linear metal-filled trenchesarranged parallel to one another within a dielectric material. Thetrenches may be arranged in groups where trenches within a group are inclose proximity to one another and multiple groups are arranged to formthe substrate structure. The metal in these trenches is electricallyisolated from the various devices, such as transistors, and may not haveany function in the finished IC. Substrate structures may optionally bepositioned in kerf lines between individual dies on the semiconductorsubstrate. The accuracy of imaging substrate structures is at leastpartially dependent on the contrast between the materials and thebackground material of the partially fabricated IC. Higher contrast canimprove the accuracy of imaging of the substrate structure and thus theaccuracy of alignment between the various layers.

SUMMARY

A first aspect of this disclosure is directed to a substrate structurefor an integrated circuit (IC) structure, including: a first dielectriclayer positioned above a semiconductor substrate; a first plurality oftrenches extending at least partially into the first dielectric layerfrom an upper surface of the first dielectric layer; and a first metalformed within the first plurality of trenches, wherein a spatialarrangement of the first plurality of trenches causes coupling ofsurface plasmons in the first metal to at least one wavelength of anincident light.

A second aspect of this disclosure is directed to a substrate structurefor an integrated circuit (IC) structure including: a first markingregion including: a first trench having a longitudinal orientation andformed on an upper surface of a semiconductor substrate, wherein thefirst trench has a substantially triangular cross-section and whereineach side of the first trench tapers inwardly towards a first lower tip;a second trench having the longitudinal orientation and formed on theupper surface of the semiconductor substrate, wherein the second trenchextends substantially in parallel with the first trench, and wherein thesecond trench has a substantially triangular cross-section, and whereineach side of the second trench tapers inwardly towards a second lowertip; a ridge formed on the upper surface of the semiconductor substrate,wherein the ridge is positioned directly between the first trench andthe second trench, and wherein the ridge extends substantially inparallel to both trenches, and wherein the ridge has a substantiallytriangular cross-section, and wherein each side of the ridge tapersinwardly towards an upper tip; and a metal formed in the first andsecond trenches of the first marking region.

A third aspect of this disclosure is directed to a method of detectingoverlay alignment when fabricating an integrated circuit (IC) structure,the method including: providing a substrate structure, the substratestructure including: a first dielectric layer positioned above asemiconductor substrate; a first plurality of trenches within an uppersurface of the first dielectric layer; and a first metal within thefirst plurality of trenches, wherein a spatial arrangement of the firstplurality of trenches causes coupling of surface plasmons in the firstmetal to at least one wavelength of an incident light; illuminating thesubstrate structure with a light source including wavelength componentswhich couple with surface plasmons in the first metal, and wherein theilluminating yields focused plasmons within the substrate structure; anddetecting the overlay alignment by detecting the incident lightreflected from the substrate structure.

The foregoing and other features of this disclosure will be apparentfrom the following more particular description of embodiments of thisdisclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments of this disclosure will be described in detail, withreference to the following figures, wherein like designations denotelike elements.

FIG. 1 shows a plan view in plane X-Y of a substrate structure accordingto embodiments of the disclosure.

FIG. 2 shows a cross-sectional view in plane X-Z of a substratestructure being illuminated according to embodiments of the disclosure.

FIG. 3 shows a plan view in plane X-Y of a substrate structure with twovertically aligned layers according to embodiments of the disclosure.

FIG. 4 shows a cross-sectional view in plane X-Z of a substratestructure with two vertically aligned layers according to embodiments ofthe disclosure.

FIG. 5 shows a plan view in plane X-Y of a substrate structure with twovertically aligned and oppositely oriented layers according toembodiments of the disclosure.

FIG. 6 shows a plan view in plane X-Y of a substrate structure spatialarrangement with multiple quadrilateral trenches according toembodiments of the disclosure.

FIG. 7 shows a plan view in plane X-Y of a substrate structure spatialarrangement with multiple rounded trenches according to embodiments ofthe disclosure.

FIG. 8 shows a plan view in plane X-Y of a substrate structure spatialarrangement with multiple trench segments according to embodiments ofthe disclosure.

FIG. 9 shows a plan view in plane X-Y of a substrate structure spatialarrangement with inwardly tapered lateral sidewalls according toembodiments of the disclosure.

FIG. 10 shows a plan view in plane X-Y of a substrate structure spatialarrangement with substantially elliptical trenches according toembodiments of the disclosure.

FIG. 11 shows a plan view in plane X-Y of a substrate structure spatialarrangement with multiple quadrilateral trenches and trench segmentsaccording to embodiments of the disclosure.

FIG. 12 shows a plan view in plane X-Y of a marking region for asubstrate structure with substantially triangular trenches and ridgesaccording to embodiments of the disclosure.

FIG. 13 shows a cross-sectional view in plane X-Z of a marking regionfor a substrate structure with substantially triangular trenches andridges according to embodiments of the disclosure.

FIG. 14 shows a plan view in plane X-Y of a substrate structure withmultiple marking regions according to embodiments of the disclosure.

FIG. 15 shows a cross-sectional view in plane X-Y of a substratestructure with multiple marking regions according to embodiments of thedisclosure.

It is noted that the drawings of this disclosure are not to scale. Thedrawings are intended to depict only typical aspects of this disclosure,and therefore should not be considered as limiting the scope of thisdisclosure. In the drawings, like numbering represents like elementsbetween the drawings.

DETAILED DESCRIPTION

In the following description, reference is made to the accompanyingdrawings that form a part thereof, and in which is shown by way ofillustration specific representative embodiments in which the presentteachings may be practiced. These embodiments are described insufficient detail to enable those skilled in the art to practice thepresent teachings and it is to be understood that other embodiments maybe used and that changes may be made without departing from the scope ofthe present teachings. The following description is, therefore, merelyillustrative.

This disclosure relates to integrated circuit (IC) structures andfabrication techniques. More particularly, the present disclosurerelates to a substrate structure for an IC structure and methods ofusing the same to provide, e.g., improvements to image contrast,detectability, etc., as compared to conventional substrate structures.Integrated circuits are manufactured employing, among other operations,multiple processing steps that selectively add or remove material in oneor more layers formed on a semiconductor substrate. Certain processingsteps may entail multiple addition or removal operations on the samelayer. Alternatively or additionally, multiple layers may be affected bya single operation or series of operations. Fabrication of functionaland reliable ICs depends at least partially on accurate alignmentbetween each of these layers and between each of the operationsperformed upon the layers.

Accurate alignment between design layers and mask layers may beaccomplished by several means. One of these is forming one or moresubstrate structures on the partially fabricated IC as it is beingprocessed. Processing equipment may image the substrate structure(s) toadjust alignment during processing, or may image substrate structuresafter a series of fabrication operations to detect if misalignedfeatures are present. One type of substrate structure that is known inthe art is composed of several linear metal-filled trenches arrangedparallel to one another within a dielectric material.

Conventional methods of forming metal substrate structures can producetrenches with metal fills that are not thick enough to produce goodcontrast against the background when imaged. Conventional methods mayalso produce trenches that lack uniformity. Weak contrast ornon-uniformity can cause unreliable results when measuring alignment,resulting in defective product or leading to expensive andtime-consuming re-work operations. Embodiments of the present disclosureprovide for a distinct spatial arrangement of trenches, and metaltherein, to provide stronger image contrast at one or more locations ina substrate structure. Although the present disclosure contemplatesembodiments of a substrate structure with varying types of spatialarrangements, each substrate structure discussed herein is structured toinclude sharp corners, edges, and other geometrical features whichconcentrate light at a particular point or region of metal. Thisconcentration of light may allow for coupling of surface plasmons inmetal to incident light, and thus may improve the detectability of asubstrate structure. The various embodiments described herein mayincrease the accuracy of alignment during fabrication, increasing yieldand decreasing costs.

Referring to FIGS. 1 and 2 together, a substrate structure 100 accordingto embodiments of the disclosure is shown. Substrate structure 100 maytake a variety of forms, usable together or separately, as described indetail herein to enhance image contrast during analysis of a circuitstructure formed to include substrate structure(s) 100 therein.Substrate structure 100 may be embedded within, e.g., a functional ornon-functional region of a larger IC device. According to someembodiments, substrate structure 100 may be configured for removalduring process steps after detection of substrate structure(s) 100,e.g., by being located within or proximal to a scribe line whereindividual die are separated from a larger wafer structure. Embodimentsof the disclosure may take advantage of physical phenomena arising fromthe interaction between particular wavelengths of light and one or moresurfaces of a metal structure. In particular, embodiments of thedisclosure rely upon the excitation of surface plasmons in a particularmetal to improve the reflectivity, detection, etc., of one or morestructures in an substrate structure.

The overall structure of substrate structure 100 may include a spatialarrangement, defined herein as a combination of one or more shapes,sizes, orientations, etc., of metal components and trenches in substratestructure 100 configured to induce the coupling of surface plasmons toat least one wavelength of incident light transmitted to substratestructure 100. The spatial arrangement of metals in substrate structure100 may be selected to increase the reflectivity of substrate structure100 and its components, e.g., by using surface plasmons in the metal toprovide greater reflectivity than may be available in conventionalsubstrate structures. In addition, the individual shapes, geometricalprofiles, etc., of each spatial arrangement for substrate structure 100may be chosen to enable the multiplication of plasmon momentum fromlarger-volume metals to smaller-volume metals. These characteristics ofsubstrate structure 100 may focus plasmon formation on metal surfaces,and increase the intensity of reflected light. Thus, substrate structuremay behave similarly to a diffraction grating configured to direct lightenergy toward smaller regions of metal, where incident light will moreeasily couple to and excite surface plasmons on particular surfaces orregions of the metal.

To better illustrate the various embodiments of substrate structure 100,an overview of surface plasmon interaction according to the presentdisclosure is provided. The term “plasmon” does not refer to aparticular particle classification, but rather denotes groups ofelectrons which behave similarly to a single particle when acted upon byparticular wavelengths of incident light. The term “surface plasmon”distinguishes surface plasmons appearing at or proximal to the surfaceof a metal or other structures from plasmons which may be buried beneathother regions, layers, etc., of a metal substance. Surface plasmons mayfurther be defined as groups of delocalized electron oscillationsinduced along the interface between two or more adjacent materials, andcreated by photonic energy entering a particular interface byinteraction with an incident light. For ease of understanding, plasmonsmay be considered for the purpose of explanation as an area ofelectronic “fluid” in a piece of conductive material that may undergoelectrical excitation upon being subjected to incident light at aparticular wavelength. The resulting surface plasmons in a metal maythemselves exhibit a particular wavelength and frequency, which maythemselves be dependent upon the wavelength(s) of light being incidentupon the surface where surface plasmons form. The resulting frequencyand wavelength of surface plasmons may ensue from attractive forcesbeing applied to the excited electrons, caused by non-excited portionsof the surface structure pulling the plasmons back to their originalpositions.

It has been determined that the frequency of some surface plasmons maybe similar to that of visible light frequencies. To this extent,embodiments of the present disclosure provide substrate structure(s) 100with spatial arrangements configured to couple surface plasmons in ametal structure to incident light. The metallic regions of substratestructure 100 may function similarly in principle to a diffractiongrating. According to an example, incident light coming into contactwith a material having a grating constant K will gain a momentum inmultiples of 2π/K in the direction of the light's periodicity, and thusallow for coupling between particular wavelengths of light andhigher-momentum surface plasmons in the metal. The coupling of surfaceplasmons to incident light, as discussed herein, is particularlydesirable in substrate structures configured for detection and analysisby illumination from an external light source. Although various spatialarrangements for substrate structure(s) 100 are described in detailherein, each of the various arrangements is linked by one or moreunderlying structural features capable of causing the aforementionedcoupling of surface plasmons to particular wavelengths of incidentlight. As will be discussed in various examples herein, substratestructure 100 may include a set of trenches, each filled with metal, inclose proximity with each other and decreasing in size along aparticular range of surface areas, volumes, etc. It may be desirable forthe various trenches and substrate structures 100 to converge upon oneor more particular light-concentrating trenches, points, etc.,representing the smallest-size element in substrate structure 100. Therelative size of such trenches, points, etc., compared to nearbyelements of increasing size, relative to the smallest element, creates afocusing effect and corresponding point of concentration for incidentlight, and thus greater image detection, contrast, etc., throughcoupling of surface plasmons in a metal to particular wavelengths ofincident light. It is therefore understood that although substratestructure(s) 100 are discussed throughout the disclosure with particulartypes of underlying spatial arrangements, each embodiment of substratestructure(s) 100 is configured to provide coupling between surfaceplasmons in a metal at a smallest-size element to at least onewavelength of incident light.

In light of the above discussion of interaction between incident lightand surface plasmons, methods of using substrate structure 100 fordetection of overlay alignment according to the disclosure are discussedherein. Embodiments of the present disclosure include providing ansubstrate structure 100 of an integrated circuit (IC) to be illuminatedduring manufacture according to various embodiments. Referring to FIGS.1 and 2 together, FIG. 1 provides a plan view of an example substratestructure 100, while FIG. 2 provides a cross-sectional view in plane X-Zof substrate structure 100. Substrate structure 100 may include multiplelayers fabricated during previous processing steps. For example,substrate structure 100 may include a semiconductor substrate 102 (FIG.1), a first dielectric layer 104 positioned on semiconductor substrate102, a first plurality of trenches 106 each filled with a first metal108, and an external light source 110 (FIG. 2 only) positioned over andin substantial alignment with first metal 108 within first plurality oftrenches 106. Light source 110 may emit an incident light L uponsubstrate structure 100, either directly or after passing through otherlayers, materials, etc., (not shown) formed on substrate structure 100.It is understood that other materials (not shown) optionally may beincluded within or proximal to substrate structure 100, e.g., variousmasks, additional dielectric materials, liners, spacers, etc., but suchmaterials are omitted from the various FIGS. solely for clarity ofillustration.

The composition of various materials included within substrate structure100 may be the same regardless of which particular spatialarrangement(s) are used. For instance, substrate 102 may includematerials such as, e.g., silicon, germanium, silicon germanium, siliconcarbide, and those consisting essentially of one or more III-V compoundsemiconductors having a composition defined by the formulaAl_(X1)Ga_(X2)In_(X3)As_(Y1)P_(Y2)N_(Y3)Sb_(Y4), where X1, X2, X3, Y1,Y2, Y3, and Y4 represent relative proportions, each greater than orequal to zero and X1+X2+X3+Y1+Y2+Y3+Y4=1 (1 being the total relativemole quantity). Other suitable substrates include II-VI compoundsemiconductors having a composition Zn_(A1)Cd_(A2)Se_(B1)Te_(B2), whereA1, A2, B1, and B2 are relative proportions each greater than or equalto zero and A1+A2+B1+B2=1 (1 being a total mole quantity). Furthermore,the entirety of substrate 102 or various portions of substrate 102 maybe strained.

Dielectric materials of first dielectric layer 104 may include anyinterlevel or intralevel dielectric material including inorganicdielectric materials, organic dielectric materials, or combinationsthereof. Dielectric materials may have various dielectric constants (K).High-K dielectrics are employed when high capacitance is desired, andlow-K and ultra-low-K dielectrics are employed when low capacitance isdesired. Suitable dielectric materials include but are not limited to:carbon-doped silicon dioxide materials; fluorinated silicate glass(FSG); organic polymeric thermoset materials; silicon oxycarbide; SiCOHdielectrics; fluorine doped silicon oxide; spin-on glasses;silsesquioxanes, including hydrogen silsesquioxane (HSQ), methylsilsesquioxane (MSQ) and mixtures or copolymers of HSQ and MSQ;benzocyclobutene (BCB)-based polymer dielectrics, and anysilicon-containing low-k dielectric. Examples of spin-on low-k filmswith SiCOH-type composition using silsesquioxane chemistry include HOSP™(available from Honeywell), JSR 5109 and 5108 (available from JapanSynthetic Rubber), Zirkon™ (available from Shipley Microelectronics, adivision of Rohm and Haas), and porous low-k (ELk) materials (availablefrom Applied Materials). Examples of carbon-doped silicon dioxidematerials, or organosilanes, include Black Diamond™ (available fromApplied Materials) and Coral™ (available from Lam Research). An exampleof an HSQ material is FOx™ (available from Dow Corning).

First plurality of trenches 106 of substrate structure 100 may be formedaccording to any process or combination of processes suitable to formtrenches within only targeted regions of first dielectric layer 104.First plurality of trenches 106 in embodiments of substrate structure100 may differ from similar openings, trenches, etc., in substratestructures by having a spatial arrangement suitable for the coupling ofsurface plasmons in first metal 108 to particular wavelengths ofincident light. Regardless of these structural characteristics of firstplurality of trenches 106, first plurality of trenches 106 may be formedby any currently known or later developed process of forming trencheswithin a dielectric material. For instance, one or more masks (notshown) may be formed on the top of first dielectric layer 104 duringmanufacture to cover non-targeted portions of first dielectric layer104, allowing other portions of first dielectric layer 104 to be removedby etching. The mask(s) then may be removed to expose the upper surfaceof first dielectric layer 104 with first plurality of trenches 106. Thevarious spatial arrangements described herein may be formed, e.g., bychanging the mask(s) used to form first plurality of trenches 106.

First metal 108 deposited in first plurality of trenches 106 can be inthe form of any currently known or later developed conductive materialsuch as, e.g., aluminum (Al), zinc (Zn), indium (In), copper (Cu),indium copper (InCu), silver (Ag), ruthenium (Ru), tin (Sn), tantalum(Ta), tantalum nitride (TaN), tantalum carbide (TaC), titanium (Ti),titanium nitride (TiN), titanium carbide (TiC), tungsten (W), tungstennitride (WN), tungsten carbide (WC), cobalt (Co), and/or polysilicon(poly-Si) or combinations thereof. However, some types of metal mayexhibit a higher tendency to permit coupling of surface plasmons in themetal to particular wavelengths of incident light. To this extent,embodiments of the disclosure include metal compositions in substratestructure 100 which may not be present in conventional substratestructures and/or not formed to have the various spatial arrangementsdiscussed herein. Such metals particularly suitable for use as firstmetal 108 may include, e.g., copper (Cu), silver (Ag), ruthenium (Ru),and/or other metals or metal-based substances suitable for the creationof, or use within, metal-to-dielectric interfaces where surface plasmonsin the metal may be coupled to particular wavelengths of incident light.

Methods according to the disclosure may include providing substratestructure 100 with a spatial arrangement configured for coupling surfaceplasmons in first metal 108 to at least one wavelength of incident light(e.g., in the arrangement shown in FIGS. 1, 2 or any of the variousarrangements discussed herein), followed by illuminating substratestructure 100 with incident light L from light source 110. As a resultof the various physical phenomena discussed herein, illuminatingsubstrate structure 100 with incident light L from light source 110 mayyield focused plasmons at the surface of first metal(s) 108 withinsubstrate structure 100. According to the example of FIG. 1, firstplurality of trenches 106 includes first metal(s) 108 formed therein,with the various regions of first metal 108 being substantially linearand having a linearly decreasing set of lengths. One first metal 108(positioned furthest to the left on X-axis), for example, may have alength L1 greater than all other first metals 108 in first plurality oftrenches 106. By contrast, another first metal 108 (positioned furthestto the right on X-axis) may have a length L2 that is less than all otherfirst metal 108 in first plurality of trenches 106. Each successivefirst metal 108 from left to right in first plurality of trenches 106may exhibit a decreasing length along a particular profile, e.g., untilreaching the rightmost first metal 108 with length L2. The spatialarrangement of first metals 108 in first plurality of trenches 106 thusfocuses light onto the rightmost first metal 108, and allows coupling ofsurface plasmons in the rightmost first metal 108 to particularwavelengths of incident light. Thus, the shining of incident light Lfrom light source 110 on substrate structure 100 may cause surfaceplasmons within first metal(s) 108 to be coupled to particularwavelengths of incident light L for greater detectability of substratestructure 100 within a larger IC structure. Although light source 110and incident light L are not shown in the various plan views herein, itis understood that each embodiment of substrate structure 100 may bepositioned in alignment with light source 110 and incident light Lemitted therefrom.

To implement methods according to the disclosure, the settings of lightsource 110 may be adjustable to yield forms of incident light L capableof inducing greater coupling between surface plasmons of first metal 108and particular wavelengths of incident light L. According to anembodiment, light source 110 may be selected, configured, etc., to havea wavelength suitable for resonance between the applied incident light Land surface plasmons of first metal 108 when the emitted incident lightL is at its highest possible intensity. Stronger resonance betweenincident light L and first metal 108 may, in some cases, create focusedplasmons within first metal 108 of substrate structure 100. Tofacilitate such a response from first metal(s) 108, light source 110 maybe substantially monochromatic (i.e., capable of producing only a subsetof wavelengths or colors) to induce resonance between incident light Land first metal 108. Wavelengths of incident light L appropriate forcausing surface plasmons of first metal 108 to couple with incidentlight L may include, e.g., light having a wavelength betweenapproximately four-hundred nanometers (nm) to approximatelyseven-hundred nm.

The position and/or orientation of light source 110 may also beadjustable to create stronger interaction between incident light L andfirst metal 108. For instance, the position of light source 110 may beselected, adjusted, etc., to cause incident light L to be substantiallyperpendicular to the uppermost surface of substrate structure 100 (e.g.,the substantially planar upper surface of first dielectric layer 104 andfirst metal 108). According to further examples, an incident angle ofillumination (measured, e.g., relative to the planar upper surface offirst dielectric layer 104 and first metal 108) between incident light Land substrate structure 100 may be between approximately five degrees toapproximately ninety degrees (i.e., a substantially perpendicularangle). In another subset of embodiments, incident light L may simply bepositioned for reflection and detection of at least some incident lightL from substrate structure 100.

Proceeding to FIGS. 3 and 4, further embodiments of substrate structure100 according to the present disclosure are discussed. The variouscomponents of substrate structure 100 described herein relative to FIGS.1 and 2 may form one of multiple reflective elements in a largerstructure for determining whether multiple layers of an IC structure arein substantial alignment. According to further embodiments, one or moreintermediate layers 112 (FIG. 4 only) may be positioned on or abovefirst dielectric layer 104 and/or first metal(s) 108. Intermediatelayer(s) 112 may include one or more semiconductor materials describedelsewhere herein, and according to further examples may include one ormore of dielectric materials, metals, and/or other materials includedwithin an IC device between various layers or regions of dielectricmaterial. A single intermediate layer 112 is shown in FIG. 4 for thepurposes of example, but it is understood that multiple intermediatelayers 112 may be included in substrate structure 100 according tovarious embodiments of the disclosure. A second dielectric layer 114having, e.g., the same composition as first dielectric layer 104 orother dielectric materials may be positioned on intermediate layer(s)112. Second dielectric layer 114 may have a second plurality of trenches116 formed therein.

As discussed in further detail elsewhere herein, second plurality oftrenches 116 may exhibit the same spatial arrangement as first pluralityof trenches 106, or may exhibit a different spatial arrangement to suitvarious applications and/or light detection techniques. In any case,second plurality of trenches 116 may be filled with a second metal 118.Second metal 118 may include the same metal as first metal 108 or adifferent metallic substance, and may have an upper surfacesubstantially coplanar to that of second dielectric layer 114. Incidentlight L from light source 110 thus may be positioned for coupling tosurface plasmons in first and second metals 106, 116. It is alsounderstood that further embodiments of substrate structure 100 mayinclude several additional intermediate layers, dielectric layers,trenches, and metals in addition to intermediate layer 112, seconddielectric layer 114, second plurality of trenches 116, second metal(s)118, to provide detection of multiple layers, regions, etc., of an ICstructure. In any case, first and second metals 108, 118 may besubstantially vertically aligned with each other, e.g., such that one ormore trenches in second plurality of trenches 116 are positioneddirectly over a corresponding trench of first plurality of trenches 106.Substantial alignment between first and second pluralities of trenches106, 116 may allow incident light L from the same light source 110 toexcite surface plasmons in first and second metals 108, 118 of substratestructure 100.

Referring to FIGS. 4 and 5 together, some embodiments of substratestructure 100 may include first and second pluralities of trenches 106,116 with varying orientations. In the plan view of FIG. 5, firstplurality of trenches 106 and first metal(s) 108 therein are shown byphantom lines to denote their positions beneath the solid line depictionof second plurality of trenches 116 and second metal(s) 118 therein. Inthe example of FIG. 4, each plurality of trenches 106, 116 and metal(s)108, 118 have a same shape and orientation, thereby focusing incidentlight onto the right side of substrate structure 100 along X-axis. Thatis, they are aligned over one another as shown in FIG. 3. In theadditional example of FIG. 5, each plurality of trenches 106, 116 isstructured to concentrate light at one region of metal 106, 108 atopposite locations. Thus, first plurality of trenches 106 is structuredto concentrate light at a location opposite that of second plurality oftrenches 116, e.g., by the smallest region of metal(s) 108, 118 in eachplurality of trenches 106, 116 being positioned at opposite endsrelative to each other. In the example of FIG. 5, the leftmost firstmetal 108 in first plurality of trenches 106 has the smallest length andthus provides the greatest concentration of surface plasmons in firstplurality of trenches 106, while the rightmost second metal 118 servesthis function in second plurality of trenches 116. The arrangement ofFIG. 5 may be preferable in some instances for detecting where substratestructure 100 is formed within each layer where remaining portions ofsubstrate structure 100 have significant surface contrast withoutrelying solely on the coupling of surface plasmons to incident light.

Turning now to FIGS. 6 and 7, further embodiments of the disclosureinclude forming first plurality of trenches 106 to have a spatialarrangement for focusing light at a center of substrate structure 100.According to this example, most of first plurality of trenches 106 mayexhibit a looped shape. As discussed in further detail herein, it isunderstood that the smallest regions of first metal(s) 108 in substratestructure 100 may be positioned laterally within the interior of otherfirst metal(s) 108 having a hollow interior and larger perimeter orcircumference than first metal(s) 108 enclosed therein. It is alsounderstood that each of the various embodiments of substrate structure100 may be formed in multiple layers, e.g., as discussed relative toFIGS. 3-5 herein, and that only first plurality of trenches 106 is shownfor clarity of illustration.

FIGS. 6 and 7 provide embodiments of substrate structure 100 in whichfirst plurality of trenches 106 includes four trenches 120 a, 120 b, 120c, 120 d each having a respective region of first metal 108 therein,denoted separately in each figure as regions 108 a, 108 b, 108 c, 108 d,and positioned within first dielectric layer 104. The embodiments ofsubstrate structure 100 shown in FIGS. 6 and 7 and discussed herein arestructured to focus light onto the innermost regions of first metal 108in first dielectric layer 104 by a spatial arrangement in which firstplurality of trenches 106 form a bull-eye type arrangement of firstmetal(s) 108. First metal 108 a of first trench 120 a, the innermostregion of metal, is formed within a trench to have a substantiallyquadrilateral (FIG. 6) or rounded (FIG. 7) profile and an outerperimeter (FIG. 6) or outer circumference (FIG. 7). First metal 108 aand first trench 120 a may be laterally enclosed within portions offirst dielectric layer 104 and structurally isolated from first metals108 b, 108 c, 108 d, and trenches 120 b, 120 c, 120 d as shown. Secondtrench 120 b with a portion of first metal 108 b therein may alsoexhibit a substantially quadrilateral profile (FIG. 6) or roundedprofile (FIG. 7) centered about and a hollow lateral interior forenclosing first metal 108 a of first trench 120 a and portions of firstdielectric layer 104 laterally therein. As shown, second trench 120 bmay be positioned laterally outside the perimeter (FIG. 6) orcircumference (FIG. 7) of first trench 120 a where first metal 108 a isformed. Substrate structure 100 may further include one or more regionsof first metal identified as 108 c, 108 d within a third trench 120 cand a fourth trench 120 d, respectively. Trenches 120 c, 120 d in turnmay be positioned laterally outside of first metals 108 a, 108 b andcorresponding portions of first dielectric layer 104. Each region offirst metal 108 a, 108 b, 108 c, 108 d and their corresponding trenches120 a, 120 b, 120 c, 120 d are formed to be substantially concentricwith each other. Thus, substrate structure 100 may include multipletrenches 120 a, 120 b, 120 c, 120 d and corresponding first metals 108a, 108 b, 108 c, 108 d arranged to focus light onto first metal 108 a offirst trench 120 a, i.e., the laterally innermost region of metal insubstrate structure 100.

Turning to FIG. 8, embodiments of the disclosure provide otherarrangements of trenches 120 a, 120 b, 120 c configured to focusincident light onto portions of first metal 108 a within a first trench120 a positioned at the laterally innermost location of substratestructure 100. In this case, first trench 120 a is not wholly laterallyenclosed by second and third trenches 120 b, 120 c. Instead, each trench120 a, 120 b, 120 c is shown to be oriented substantially along a sharedaxis S-S, with first trench 120 a being positioned between pairs ofsecond trenches 120 b and third trenches 120 c. According to anembodiment, first plurality of trenches 106 may include first trench 120a having a first length C1, second trench 120 b extending substantiallycoaxially with first trench 120 a and having a second length C2, andthird trench 120 c extending substantially coaxially with trenches 120a, 120 b and having a third length C3. As shown, the laterally innermosttrench 120 a with first metal 108 a therein may have the smallest of thethree lengths C1, C2, C3 along X-axis. Furthermore, first trench 120 amay be positioned substantially equidistantly between second trenches120 b, such that a substantially same lateral thickness of firstdielectric layer 104 separates first trench 120 a from second trenches120 b. Second trenches 120 b may similarly be positioned equidistantlybetween first trench 120 a and one third trench 120 c.

Turning to FIG. 9, another spatial arrangement of substrate structure100 according to embodiments of the disclosure is shown. In the exampleof FIG. 9, regions of first metal 108 a, 108 b are formed respectivelywithin first trench 120 a and second trench 120 b. Trenches 120 a, 120 bmay each be one of a corresponding pair, and may feature an inwardlytapered shape to focus light to innermost portions of each pair of firstmetal regions 108 a, 108 b of substrate structure 100. First and secondtrenches 120 a, 120 b are shown by example as having a substantiallytriangular shape in plane X-Y, but this is not necessarily the case inall embodiments. More generally, first and second trenches 120 a, 120 bmay feature inwardly tapered lateral sidewalls which meet at aconvergence point P positioned proximate the other trench 120 a, 120 bof a given pair. The laterally tapered sidewalls of each trench 120 a,120 b may be positioned proximate each other, e.g., are only separatedfrom each other by portions of first dielectric layer 104 and no otherintervening portions of first metal(s) 108 a, 108 b. To maintain theexcitation of surface plasmons in first metal(s) 108 a, 108 b asdiscussed herein, pairs of first and second trenches 120 a, 120 b maynot intersect with each other in the embodiment of FIG. 9.

Turning to FIG. 10, embodiments of substrate structure 100 may includegroups or pairs of trenches 120 a, 120 b, 120 c, 120 d withsubstantially rounded geometries in place of laterally taperedsidewalls. As shown in FIG. 10, a pair of first and second trenches 120a, 120 b and regions of first metal 108 a, 108 b therein may exhibit asubstantially rounded or elliptical shape. In the case of an ellipticalshape, each first trench 120 a, 120 b may have a major axis and a minoraxis in plane X-Y. Pairs of trenches 120 a, 120 b and the regions offirst metal 108 a, 108 b may be substantially coaxial with each otheralong a particular axis, e.g., the major or minor axis in the case ofelliptical trenches 120 a, 120 b. Similar to other embodiments, firstand second trenches 120 a, 120 b may not intersect with each other andthus may be separated by an intervening lateral portion of firstdielectric layer 104. In any case, pairs of trenches 120 a, 120 b may bepositioned such that an arc of one trench 120 a curves toward the arc ofanother trench 120 b, thereby focusing light to the lateral ends wheretrenches 120 a, 120 b are closest to each other.

With continued reference to FIG. 10, another spatial arrangement oftrenches 120 a, 120 b, 120 c, 120 d in substrate structure 100 isdescribed for the sake of example. According to a further example,trenches 120 a, 120 b, 120 c, 120 d may be provided in a group of four,with each trench 120 a, 120 b, 120 c, 120 d having a region of firstmetal 108 a, 108 b, 108 c, 108 d formed therein. Where four trenches 120a, 120 b, 120 c, 120 d with rounded or elliptical shapes are included,two of the four trenches 120 a, 120 b may be substantially aligned witheach other along a first axis (e.g., in parallel with X-axis as shown inFIG. 10). Another two of the four trenches 120 c, 120 d may be orientedsubstantially perpendicularly with respect to trenches 120 a, 120 b andsubstantially aligned with each other along another axis (e.g., inparallel with Y-axis as shown FIG. 10). Notwithstanding the presence oftwo additional trenches 120 c, 120 d, trenches 120 a, 120 b, 120 c, 120d and regions of first metal 108 a, 108 b, 108 c, 108 d formed thereinmay not physically intersect with each other. Thus, substrate structure100 may focus light toward portions of each trench 120 a, 120 b, 120 c,120 d positioned closest to the other trenches 120 a, 120 b, 120 c, 120d in substrate structure 100.

Turning to FIG. 11, it is emphasized that the various embodiments ofsubstrate structure 100 may be used together and/or combined to includevarious features discussed herein relative to one or more otherembodiments of substrate structure 100. FIG. 11, as an example, combinesthe features discussed elsewhere herein relative to FIGS. 6 and 8 into asingle embodiment of substrate structure 100. According to an example,first plurality of trenches 106 may include coaxially-aligned rows offirst trenches 120 a, 120 b, 120 c in substantially quadrilateraloutline and with successively smaller perimeters based on proximity tothe lateral center of substrate structure 100. According to the exampleof FIG. 11, each first trench 120 a in a particular row may be alignedwith and positioned directly between a pair of second trenches 120 b,and furthermore may be substantially equidistant from each second trench120 b. Second trenches 120 b themselves may be positioned directlybetween, and equidistant from, first trench 120 a and one third trench120 c. The various sets of trenches 120 a, 120 b, 120 c with regions offirst metal 108 a, 108 b, 108 c therein may be arranged in quadrilateralsets having gradually decreasing perimeters. A centermost portion ofsubstrate structure 100 may include one or more first trenches 120 a forfocusing light from regions of first metal 108 a, 108 b, 108 c insurrounding trenches 120 a, 120 b, 120 c and thus allowing forwavelengths of incident light to be coupled to surface plasmons near thecenter of substrate structure 100. Though rectangular trenches 120 a,120 b, 120 c and quadrilateral groups of trenches 120 a, 120 b, 120 care shown by example in FIG. 11, it is understood that rounded,triangular, and/or other geometrical profiles may be used in place ofthe specific profiles and/or spatial arrangements shown by example inFIG. 11.

Referring now to FIGS. 12 and 13, embodiments of substrate structure 100may be structured for focusing light in a vertical direction to providecoupling of incident light to surface plasmons at vertical ends of firstmetal 108. Such embodiments may be used in addition to or in place ofother embodiments discussed herein, e.g., which may be structured forcoupling of incident light to surface plasmons at lateral ends of firstmetal(s) 108. FIG. 12 provides a plan view in plane X-Y of substratestructure 100 according to further embodiments, while FIG. 13 provides across-sectional view of the same embodiment of substrate structure 100in plane X-Z. Embodiments of substrate structure 100 additionally may begrouped into one or more marking regions 150 as discussed herein, e.g.,to provide several regions each configured to couple incident light withsurface plasmons in substrate structure 100. A single marking region 150is shown in FIGS. 12 and 13, while other embodiments of substratestructure 100 with multiple marking regions 150 are shown in FIG. 14 anddiscussed elsewhere herein.

Substrate structure 100 may include, e.g., first plurality of trenches106 each having region of first metal 108 therein. First plurality oftrenches may include at least one first trench 120 a and at least onesecond trench 120 b each with a longitudinal orientation (e.g.,substantially parallel with Y-axis in FIG. 12). First and secondtrenches 120 a, 120 b may be positioned directly laterally adjacent toeach other, and it is possible for portions of first metal 108 in eachtrench 120 a, 120 b to contact each other at an upper surface of firstdielectric layer 104. First and second trenches 120 a, 120 b may exhibita substantially triangular cross-section as shown specifically in FIG.13. The various trenches 120 a, 120 b in substrate structure 100 mayfurther include a substantially horizontal base located on one verticalend of first dielectric layer 104, and a tip (e.g., a convergence ofinwardly tapered sidewalls) at their opposing vertical ends. Accordingto the example of FIG. 13, each trench 120 a, 120 b may have avertically-downward orientation, but it is understood that opposingvertical orientations are possible in further embodiments of thedisclosure. The inward tapering of each trench 120 a, 120 b and firstmetal(s) 108 formed therein may be configured for the coupling ofsurface plasmons in first metal(s) 108 to particular wavelengths ofincident light L. Specifically, the gradual reduction in trench widthmay allow for focusing of incident light L at the vertical tip of eachtrench 120 a, 120 b and an associated coupling of surface plasmons infirst metal 108 to incident light L.

The structural configuration of trenches 120 a, 120 b and first metal108 therein may determine the shape of nearby portions of firstdielectric layer 104. First and second trenches 120 a, 120 b beingpositioned directly adjacent to each other may form, e.g., a ridge Rwithin first dielectric layer 104. Ridge R, as shown in FIG. 13, mayexhibit a substantially triangular cross-section with an oppositeorientation to that of trenches 120 a, 120 b. In this case, ridge(s) Rmay feature a tip 152 positioned at or near the upper horizontal surfaceof first dielectric layer 104 due to the tapered sidewalls of eachtrench 120 a, 120 b. Where multiple substantially triangular trenches120 a, 120 b appear in substrate structure 100, one ridge R may appearin first dielectric layer 104 between first metals 108 of each pair oftrenches 120 a, 120 b. As noted above, it is possible for tip 152 ofridge(s) R to be positioned vertically beneath the upper horizontalsurface of first dielectric layer 104.

Referring now to FIGS. 12-15, a single group of trenches 120 a, 120 band first metal 108 formed therein may constitute a single markingregion 150 of substrate structure 100 as discussed elsewhere herein.According to an embodiment, one marking region 150 may be defined asincluding all trenches 120 a, 120 b and region of first metal 108 havingthe same lateral orientation (i.e., in plane X-Y). To provide morerobust detectability of substrate structure 100, embodiments of thedisclosure contemplate forming multiple marking regions 150 a, 150 b,150 c, 150 d (FIGS. 14, 15 only) in a single substrate structure 100.According to an example, each marking region 150 a, 150 b, 150 c, 150 dmay include several groups of paired trenches 120 a, 120 b (identifiedseparately in FIGS. 12, 13) each having regions of first metal 108formed therein. The various trenches 120 a, 120 b in each marking region150 a, 150 b, 150 c, 150 d may exhibit a substantially triangularcross-section as noted elsewhere herein.

One or more marking regions 150 may have a different longitudinalorientation from that of other marking regions. For instance, markingregions 150 a, 150 b are each shown to have a respective plurality oftrenches 106 a, 106 b oriented along the same axis (e.g., in parallelwith X-axis), while being located in different areas of first dielectriclayer 104 and/or substantially in parallel with each other. Othermarking regions 150 c, 150 d, are shown by example to have substantiallythe same lateral surface area as marking regions 150 a, 150 b butdifferent lateral orientations. Marking regions 150 c, 150 d may beoriented substantially perpendicularly with respect to marking regions150 a, 150 b (e.g., in parallel with Y-axis), but substantially inparallel with each other. Each marking region 150 a, 150 b, 150 c, 150 dmay include a set of ridges R (FIG. 13 only) directly between each pairof trenches 120 a, 120 b (FIGS. 12, 13) as discussed elsewhere herein.As also shown in FIG. 14, it is possible to include a larger amount ofseparation between two or more regions of first metal 108, e.g., suchthat each plurality of trenches 106 a, 106 b, 106 c, 106 d may besubdivided into groups of two, four (as shown in FIG. 14), six, etc.Substrate structure 100 according to the disclosure thus may includefirst pluralities of trenches 106 and first metal(s) 108 therein, andwith various spatial arrangements for coupling surface plasmons in firstmetal(s) 108 to one or more wavelengths of incident light.

It is again emphasized that the various embodiments of substratestructure 100 discussed herein and illustrated in FIGS. 1-14 are notlimited to a single type of spatial arrangement, or being formed in onlyone layer of a particular IC structure. For example, it is possible toform and use an embodiment of substrate structure 100 in every singledistinct layer of an IC structure, and in multiple locations within thesame layer of a particular structure. Furthermore, it is possible forone or more embodiments of substrate structure 100 to be placed insubstantial vertical alignment with a similar or different embodiment ofsubstrate structure 100 in a different layer of the same IC structure.Various embodiments substrate structure 100 may also be modified toinclude still other spatial arrangements configured for coupling ofsurface plasmons in first metal 108 and/or other metals of differentlayers to particular wavelengths of incident light. The variousembodiments of substrate structure 100 may also be combined with eachother to form still further embodiments, or selected portions ofsubstrate structure 100 may be omitted to provide a simplified markingstructure. In any case, substrate structure 100 may be operable tocouple surface plasmons in a metal substance to wavelengths of incidentlight by being structured to focus the incident light into areas with alowest length, surface area, volume, etc., in horizontal and/or verticaldirections.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of this disclosure.As used herein, the singular forms “a,” “an,” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof. “Optional” or “optionally” means thatthe subsequently described event or circumstance may or may not occur,and that the description includes instances where the event occurs andinstances where it does not.

Approximating language, as used herein throughout the specification andclaims, may be applied to modify any quantitative representation thatcould permissibly vary without resulting in a change in the basicfunction to which it is related. Accordingly, a value modified by a termor terms, such as “about,” “approximately,” and “substantially,” are notto be limited to the precise value specified. In at least someinstances, the approximating language may correspond to the precision ofan instrument for measuring the value. Here and throughout thespecification and claims, range limitations may be combined and/orinterchanged, such ranges are identified and include all the sub-rangescontained therein unless context or language indicates otherwise.“Approximately” as applied to a particular value of a range applies toboth values, and unless otherwise dependent on the precision of theinstrument measuring the value, may indicate +/−10% of the statedvalue(s). “Substantially” refers to largely, for the most part, entirelyspecified or any slight deviation which provides the same technicalbenefits of this disclosure.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below are intended toinclude any structure, material, or act for performing the function incombination with other claimed elements as specifically claimed. Thedescription of the present disclosure has been presented for purposes ofillustration and description, but is not intended to be exhaustive orlimited to this disclosure in the form disclosed. Many modifications andvariations will be apparent to those of ordinary skill in the artwithout departing from the scope and spirit of this disclosure. Theembodiment was chosen and described in order to best explain theprinciples of this disclosure and the practical application, and toenable others of ordinary skill in the art to understand this disclosurefor various embodiments with various modifications as are suited to theparticular use contemplated.

Unless otherwise noted, or as may be evident from the context of theirusage, any terms, abbreviations, acronyms or scientific symbols andnotations used herein are to be given their ordinary meaning in thetechnical discipline to which the disclosure most nearly pertains. Thefollowing terms, abbreviations and acronyms may be used throughout thedescriptions presented herein and should generally be given thefollowing meaning unless contradicted or elaborated upon by otherdescriptions set forth herein. Some of the terms set forth below may beregistered trademarks (®).

What is claimed is:
 1. A method of detecting overlay alignment whenfabricating an integrated circuit (IC) structure, the method comprising:providing a substrate structure, the substrate structure including: afirst dielectric layer positioned above a semiconductor substrate; afirst plurality of trenches within an upper surface of the firstdielectric layer; and a first metal within the first plurality oftrenches, wherein a spatial arrangement of the first plurality oftrenches causes coupling of surface plasmons in the first metal to atleast one wavelength of an incident light; illuminating the substratestructure with a light source including wavelength components whichcouple with surface plasmons in the first metal, and wherein theilluminating yields focused plasmons within the substrate structure; anddetecting the overlay alignment by detecting the incident lightreflected from the substrate structure.
 2. The method of claim 1,wherein the light source has a maximum emission at the wavelengthcomponents which resonate with the substrate structure, such that thelight source creates focused plasmons within the substrate structureduring the illuminating.
 3. The method of claim 1, wherein the lightsource is substantially monochromatic at the wavelength components whichresonate with the substrate structure such that the light source createsfocused plasmons within the substrate structure during the illuminating.4. The method of claim 1, wherein an incident angle of the illuminationis substantially perpendicular to an upper surface of the substratestructure.
 5. The method of claim 1, wherein an incident angle of theillumination is in the range of between approximately 5 degrees toapproximately 90 degrees from perpendicular relative to an upper surfaceof the substrate structure.
 6. The method of claim 1, furthercomprising: forming an intermediate layer above the substrate structure;and forming a second substrate structure on an upper surface of theintermediate layer, wherein the second substrate structure is positionedabove, and substantially vertically aligned with, the substratestructure.
 7. The method of claim 1, wherein the light source emitslight including components having a wavelength in the range of betweenapproximately 400 nanometers (nm) to approximately 700 nm.